For the past year, I've been working on Data Points: Visualization that Means Something, and you can pre-order it now.
Visualization has grown a lot in the 5-something years I've written for FlowingData. It's not just a tool for analysis anymore. Visualization is a way to express data, and it comes in the form of information graphics, entertainment, everyday interfaces, data art, and yeah, tools, too. Your approach to data and visualization changes based on application.